Tyler Cowen asks if we should subsidize or tax research into time travel. Here's my favorite comment, by "dirk":
If time-travel were possible and humans discover how to do it, the odds are greater that it has already been discovered, so to speak, in the future than that we'd discover it in the near-term present, regardless of subsidies. Therefore, the time-travelers are already here if they are going to ever be here. So instead of subsidies we should offer a huge prize for a time-traveler to tell us how it works. Even if some *future* time-traveler isn't in the present now to hear about the prize directly, if we make the prize big enough it will be discovered in the historical record and someone will claim it.The question then is: what do you get the time-traveler who has everything? Perhaps Obama should hold a press conference and say: "Time-travelers, tell me what you want." Imagine how stupid other countries will feel if that works!
So... what could we use to temp a time traveling?
a time traveller can get anything / everything he wants from here, but not in the future. Only thing we could tempt him with is a better future, so... stricter environmental policy?
Hmm, why would access to time travel let the traveler have anything he wanted from our time? It might give him a lot of wealth, but there's plenty that money can't buy.
The universe can't remember where everything was just one second ago, much less hundreds of years. Random decay is random in both positive and negative time. Water still flows down in negative time 1/2A(t^2) The sign of time is irrelevant. But lets not let reality get in the way of a good SF story line.
Many assumptions about the future are required in this speculation. Here is just one:
Future Economy - Material wealth will still be a factor or breeding will diminish below replacement levels. So, IF material wealth is no longer a factor, then natural genetic diversity may be of great value. Manufactured genetic material may be possible, but this just means 'natural' will increase in value over time. People go missing all the time. If material wealth is still a factor in the economy, then simple gold will be useful. But not just ANY gold, it has to be gold that was lost up to the time of the time travelers departure. This is because any other procurement would disturb the existing future in which the time traveler hopes to return. So go steal gold off a doomed Spanish ship or the like...
I don't think material wealth would be of great value to a time traveler.
Maybe we could blackmail a time traveler by threatening to kill a bunch of people if the time travelers don't reveal themselves? Or by threatening to destroy the earth or something. (But if we do that then there won't BE any time travelers from the future to stop us...?)
We don't know what they want, so perhaps we should ask them?
Leave a massive monument that will last beyond our feeble civilization, and inscribe on it instructions for how to make the cross-epochal request. Maybe the instructions would have to be pictorial to allow for significant changes to language and writing. The monument could house cryogenically stored linguists and scientists who, should the future civilization successfully revive them, could attempt to convey our instructions directly.
I think I've just described the pyramids.